http://www.aptana.com/forums/viewtopic.php?t=1847&highlight=dark+theme
If, like me, you used Dr. Nic's TextMate like theme, which was broken during recent updates of Aptana, you may be interested in some colourisation files I've put together to replace Dr. Nic's.
You can download it from http://www.dave-dean.co.uk/aptana/aptana_prefs_dark_theme.zip
You will need to import the three colourisation files in the relevant parts of the Preferences dialog for ERB, HTML and CSS and import my preferences file for Ruby colourisation from the File | Import menu. (Other than some colour changes, my preferences aren't changed much from the defaults).
Note: I haven't found a way to properly colour symbols in ERB - to my mind, this should really take colourisation from the Ruby preferences.
Feel free to tweak to your hearts content and improve on it.
-Dave

